"We stand ready to receive Prime Minister May at any moment in time when they are ready."

The DUP torpedoed Mrs May's efforts to reach an agreement during her trip to Brussels on Monday, with Arlene Foster pulling her party's support over concerns at the wording of a draft text she feared would agree regulatory alignment between Northern Ireland and the Republic after Brexit.

Mrs May spoke with both the DUP leader and the Republic of Ireland's Prime Minister Leo Varadkar on Wednesday in her attempt to salvage a deal with the EU.

Her efforts appeared to be further complicated on Thursday when Foreign Secretary and Vote Leave figurehead Boris Johnson warned any Brexit deal must respect promises made during the EU referendum campaign.

"It is very, very important that whatever happens now, whatever we agree, has got to be consistent with taking back control of our laws, of our borders and our cash," he said.

Without an agreement from EU leaders at next week's European Council summit, Brexit negotiations will not move on to trade talks before the New Year.

It follows suggestions closer ties with Brussels in some economic areas have been proposed as a means of ensuring there is no hard border on the island of Ireland.

Amid the ongoing discussions between Dublin, Belfast, Brussels and London, Conservative backbencher Bernard Jenkin claimed the Irish Government was "being played like a harp" by the European Commission.

He told BBC's Radio 4 Today programme: "Dublin is being used as a proxy by the EU.

"The EU is extremely worried about setting the precedent that you can leave the EU and you can have an invisible frontier."

Mr Jenkin also warned the UK "shouldn't be allowing ourselves to be bullied into promising more and more money or giving up the goal of regulatory autonomy" after Brexit.

On the other side of the Tory divide on Brexit, prominent Remain supporter Anna Soubry has called for the Government to give MPs the power to seek an extension to negotiations if a satisfactory trade agreement isn't reached by March 2019.